In gas-liquid
contact operation, the number of ideal stages N = (xa - xb)/(xb
– xb*). This is true when the stripping factor S is
(A)
S > 1
(B)
S < 1
(C)
S = 1
(D)
S = ∞
GATE
1995
Answer: (C)
Use of raschig
rings in place of crushed stones as packing in packed beds (other things being
same)
(A)
Increases pressure drop, increases
surface area
(B)
Increases pressure drop, decrease
surface area
(C)
Decreases pressure drop, increases
surface area
(D)
Decreases pressure drop, decreases
surface area
GATE 1995
Answer: (C)
For absorbing
sparingly soluble gas in a liquid
(A)
Gas side mass transfer coefficient
should be increased
(B)
Liquid side mass transfer coefficient
should be increased
(C)
Liquid side mass transfer coefficient
should be decreased
(D)
Mass transfer coefficient must be kept
constant
GATE 1995
Answer: (B)
Mass transfer
coefficient K, according to penetration theory varies with mass diffusivity as
(A)
D0.5
(B)
D
(C)
1/D
(D)
D1.2
GATE
1995
Answer: (A)
In
a gas mixture of hydrogen and oxygen, steady state equimolar counter diffusion
is occurring at a total pressure of 100 KPa and temperature of 20°C. If the
partial pressures of oxygen at two planes 0.01 m apart, and perpendicular to
the direction of diffusion are 15 KPa and 5 KPa respectively and the mass
diffusion flux of oxygen in the mixture is 1.6×10-5 Kmol/m2.sec,
calculate the molecular diffusivity for the system.
(A)
3.90×10-5 m2/sec
(B)
4.50×10-5 m2/sec
(C)
5.51×10-5 m2/sec
(D)
6.52×10-5 m2/sec
GATE
1994
Answer: (A)
In
distillation under minimum reflux conditions, number of theoretical stages
would be
(A) one
(B) minimum
(C) infinite
(D) none of these
GATE 1993
Answer: (C)
In the absorption of a
solute gas from mixture containing inerts in a solvent, it has been found that
the overall gas transfer coefficient is nearly equal to the individual gas film
transfer coefficient. It may therefore be concluded that
(A)
The process is liquid film controlled
(B)
The gas is sparingly soluble in the
solvent
(C)
The transfer rate can be increased
substantially by reducing the thickness of the liquid film
(D)
The transfer rate can be increased
substantially by reducing the thickness of the gas film
GATE
1990
Answer: (D)
Lewis number = 1
signifies
(A)
Pr = Sc
(B)
Pr = Re
(C)
Sc = Re
(D)
Nu = Sh
GATE
1990
Answer: (A)
Minimum
number of ideal stages are required in a fractionating column when the reflux
ratio is equal to
(A) minimum reflux ratio
(B) optimum reflux ratio
(C) zero
(D) infinity
GATE
1990
Answer: (D)
NTU can be
considered as a
(A)
Performance concept of the equipment
(B)
Measure of approach to identity
(C)
Measure of difficulty of separation
(D)
Measure of departure from ideality
GATE 1989
Answer: (C)
While drying a
material from a moisture content above the critical moisture content to a
moisture content very close to the equilibrium moisture content, the surface
temperature of the solid (ignoring initial adjustment period)
(A)
Remains constant
(B)
At first remains constant and then
increases
(C)
Increases continuously
(D)
At first remains a constant and then
decreases
GATE 1989
Answer: (B)
By
increasing the reflux ratio in a binary fractionating column from minimum
reflux ratio onwards, the
(A) operating cost increases but the fixed
cost decreases continuously
(B) operating cost decreases but the fixed
cost increases continuously
(C) operating cost first decreases and then
increases but the fixed cost decreases
(D) operating cost increases but the fixed
cost first decreases and then increases
GATE 1989
Answer: (D)
In the above
problem, the air from the heater will have a humidity
(A)
Equal to 30%
(B)
Greater than 30%
(C)
Less than 30%
(D)
None of the above
GATE
1989
Answer: (C)
In an absorber
the equilibrium curve is always
(A)
Parallel to the operating line
(B)
Above the operating line
(C)
Below the operation line
(D)
Coincides with the operating line
GATE
1988
Answer: (C)
Starting
at the minimum reflux ratio, as the reflux ratio is increased for a given
separation, the fixed cost of a fractionating column
(A) increases
(B) decreases
(C) first decreases and then increases
(D) first increases and then decreases
GATE 1988
Answer: (C)
Kremser – Brown
– Souders equation is used to calculate
(A)
HTU
(B)
NTU
(C)
Plate spacing in plate column
(D)
The number of ideal plates in the plate
column
GATE
1988
Answer: (D)
At the boiling
point of a completely immiscible system of two liquids, the partial pressure of
one component in the vapour phase is
(A)
Always less than its vapour pressure at
that temperature
(B)
Always greater than its vapour pressure
at that temperature
(C)
Equal to its vapour pressure at that
temperature
(D)
Dependent on the nature and amount of
the other component in the liquid phase
GATE
1988
Answer: (C)
In a continuous
counter current packed absorber operating on very dilute concentration, the
volumetric gas mass transfer coefficient is proportional to G0.8
where G is the gas flow rate in mole/unit time per unit empty area. If G is
doubled, what will be the ratio of the height of gas transfer unit at the
increased gas flow rate to the one at the original gas flow rate. (Assume the
flow rates are below the loading point)
(A)
20.8
(B)
20.2
(C)
2-0.8
(D)
2-0.2
GATE 1988
Answer: (B)
Air with a dry
bulb temperature Td1 and a wet bulb temperature Tw1 is
passed through a heater and then through an adiabatic cooler from which it
emerges with dry and wet bulb temperature of Td2 and Tw2
respectively. Then
(A)
Always Tw1 > Tw2
and Td1 > Td2
(B)
Always Tw1 < Tw2
and Td1 > Td2
(C)
Always Tw1 > Tw2
and Td1 < Td2
(D)
Tw1 < Tw2 and Td1
can be greater than equal to or less than Td2
GATE 1988
Answer: (D)
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